Singular they - Summary

Summary

Generic they has indeterminate number:

• There's not a man I meet but doth salute me / As if I were their well-acquainted friend — Shakespeare, The Comedy of Errors, Act IV, Scene 3 (1594)

(Their can be understood equally well as referring to each man considered one at a time, or to all of them collectively.)

Epicene they has indeterminate gender:

• "It can't be true what the girls at the Rectory said, that her mother was an opera-dancer—"
  "A person can't help their birth," Rosalind replied with great liberality. — Thackeray, Vanity Fair (1848)

(The relevant person here is Becky Sharp. Thackeray has Rosalind using their as a polite circumlocution, perhaps avoiding the directness of she ... her, and generic his in a context involving only women; or perhaps with Rosalind meaning the statement to apply to people in general with Becky Sharp as an example.)

In neither case is singular they unambiguously a semantic or morpho-syntactic singular. What it actually agrees with is the plurality implicit in the indeterminacy of generic antecedents.

This is explained by David Lewis's analysis of an aspect of the logic of the semantics of natural language, now called quantificational variability effect (QVE). Broader research in the area is still active, under the name donkey pronouns.

In this kind of analysis, singular they in English is typically an example of a semantically bound variable, rather than a simple referential pronoun. It is most clearly evident in the special case of distributive constructions, where the preference many languages show for singular pronouns probably gives rise to the singular in "singular they".

Steven Pinker proposes the word they be considered to be a pair of homonyms — two different words with the same spelling and sound.

• Those ladies over there are wearing their best clothes.
• On a day like today, anyone would want to wear their best clothes.